This is a variant of Clock cache algorithm that keeps a ghost copy for an extended period of time. It could be useful for implementing shared session cache.

$ npm install hl-cache

• new HLCache([options]) Create a cache pool.

var cache = new HLCache({
	 // maximum size of the cache
	max: 2000,
	 // cache entry time-to-live in milliseconds
	lifespan: 2000
});

If the number of items in the cache pool exceeds max, the item will not be store in the cache.

• HLCache::get(key[, timestamp])

Get the value by key. timestamp is optional, it is used to indicate the time the visit comes from. If no value is provided, timestamp is set to Date.now().

• HLCache::set(key, value[, timestamp])

Set the value of key to value. timestamp is optional, it is used to indicate the time the visit comes from. If no value is provided, timestamp is set to Date.now().

• HLCache::has(key)

Check if a key is in the cache.

• length

Return total length of objects in cache.

This package use Map and es6-map to polyfill Map on old version of Node.

es6-map is install as optionalDependencies. The dependencies section of your application's package.json file must contain es6-map in order for the polyfill to work.

$ npm test

Half-life cache could (almost) guarantees consistent read in cache’s lifespan, which could be useful for implementing shared session cache.

Copyright (c) 2015 Jingwei "John" Liu

Licensed under the MIT license.